Portable steam and heat generator for pest control

ABSTRACT

The present invention describes numerous improvements in steam generating apparatus for pest control. In one aspect, an improved cart arrangement for such an apparatus is described. Other aspects include improved valves, nozzles and other improvements to increase the efficiency of the steam generating apparatus.

FIELD OF THE INVENTION

The present invention is directed to an apparatus for controlling pests among other uses, particularly vegetation or weeds using a blast of hot air and steam, hot water or hot water vapor. In particular, the present invention is directed to an apparatus having various features such as valve arrangements, output nozzles, etc. to maximize operation of the apparatus.

BACKGROUND OF THE INVENTION

The control of unwanted pests, such as vegetative growth, is utilized to improve aesthetic appearance as well as removing the noxious pests or vegetation. In the past, one of the most common methods of controlling such unwanted growth was through the application of pesticides to the vegetation. Such pesticides, particularly herbicides, were commonly applied by spraying a liquid herbicide or through spreading of powders or granules. However, in recent years the use of herbicides has met with increased resistance owing to environmental, health and safety concerns. Herbicides can contaminate soil, air, groundwater and desirable vegetation and may cause health problems to those exposed to such chemicals. In view of these problems, the use of herbicides has been restricted or in some cases completely banned in many jurisdictions.

As environmental concerns are reducing the use of pesticides, and the prohibitive costs and inefficiencies of manual weeding become apparent, the use of heat and/or steam for vegetation control is gaining popularity. Heat coagulates plant protein, destroying plant cells, disrupting vascular flow and respiration. Also waxy protective leaf coatings are removed, promoting dehydration and death of the plant. Studies have shown that exposure to 80 C. (176 F) for one second can kill vegetation. Also steam or moist heat is superior to flame or dry heat for weeding as damp air transfers heat more readily, and is easier to apply in a downward direction (hot, dry air rises and diffuses faster). Steam or moist air is less likely to cause accidental fires and thus is safer than flame or dry heat.

Recently, the use of heat to kill unwanted vegetation has been utilized and a number of apparatus to apply heat, generally in the form of hot water or steam have been proposed. Examples of such apparatus are shown in U.S. Pat. Nos. 5,385,106, 5,430,970, 5,927,601, 5,946,851, 6,029,589, 6,047,900, and 6,321,037, PCT Patent Application WO 00/22926 and New Zealand Patent Application 237,524 among others.

In my previous U.S. Pat. No. 7,100,040, the disclosure of which is incorporated herein by reference, an apparatus for directing steam, hot water or hot water vapor and hot air onto a target area was described. The apparatus included an applicator wand, having a steam generator immediately adjacent the target area within a steam head at one end of the applicator wand. The applicator wand also included trigger controls to allow for a continuous flow of water to a flash boiler located in the steam head as part of the steam generator. However, the valve arrangements illustrated in that patent were fairly complex with a number of divergent paths and individual valves.

While the apparatus described in U.S. Pat. No. 7,100,540 was effective for weed control, particularly on hard surfaces, the efficiency of operation of the apparatus was found to be less than that of traditional herbicide application.

There thus remains a need for a steam generating apparatus for pest control in particular weed control having a simpler design and operation as well as having increased efficiency compared with the prior apparatus.

SUMMARY OF THE INVENTION

In one aspect of the invention, there is provided an apparatus for generating at least one of steam, hot water and hot water vapor along with air heated by a burner for application to unwanted vegetation. The apparatus comprises a wheeled cart supporting a water container, a control module, a holder for an applicator wand and a fuel container. The applicator wand comprises a holding means and an applicator head coupled to the holding means. The applicator head comprises a housing, an inlet and an outlet to define a cavity to accept a flash boiler adjacent the outlet, the flash boiler comprising a steam generator and a burner for heating the steam generator. A first elongate hose connects the water container to a first control located on the applicator wand, the first control controlling and supplying a flow of water to the steam generator, and a second elongate hose connects the fuel container to a second control located on the applicator wand, the second control controlling and supplying a flow of fuel to the burner. Both the first and second controls are controlled by a single switch, such that when said switch is activated, fuel and water are supplied essentially simultaneously to said flash boiler and a blast of heated air and at least one of steam, superheated steam, hot water and hot water vapor is urged from the outlet to the unwanted vegetation. The control module of the wheeled cart includes a water pump to supply water to the applicator wand from the water tank, a source of energy for the water pump and control and feedback circuitry and displays to allow an operator to monitor the operating parameters of the apparatus.

In another aspect of the invention, the apparatus is provided with a plurality of flash boiler in a broad applicator head to provide a wide application to the unwanted vegetation.

In another aspect, the present invention provides for a flow control and flush valve for a steam generating apparatus for weed control, which allows for a simple means of controlling the volume of water flowing through the system. The flow control valve comprises a first fixed elliptical orifice and a second rotating elliptical orifice. The center of rotation of the second elliptical orifice is located adjacent one end of the orifice. The rotation of the rotating orifice varies the overlapping area between the fixed orifice and the rotating orifice to allow for control of the volume of water flowing through the overlapping orifices.

In another aspect of the invention there is provided a trigger control valve having a bypass channel such that a small flow of fluid passes through the valve when the valve is in the closed position.

In a further aspect of the invention the trigger control valve is provided with an inlet and outlet and a spring biased poppet, which seals the outlet when the valve is in the closed position. The sealing surface of the valve against which the poppet rests is provided with a channel to allow for a low flow of water in the closed position.

In yet another aspect of the invention there is provided a steam nozzle for a steam generating apparatus for weed control. The steam nozzle aids in diffusing the steam and accelerating the airflow through the steam generating apparatus. The steam nozzle comprises an inlet and a plurality of outlets to provide for the diffusion of the steam from the steam generating apparatus.

In yet another aspect of the invention, the steam nozzle is centrally mounted within the outlet of the steam generating apparatus by a plurality of spacers or fins located between the exterior of the steam nozzle and the interior wall of the steam head of the steam generating apparatus.

In yet another aspect of the invention, the steam generating apparatus is provided with an air blower to increase the volume of air flowing through the steam generating apparatus to increase the combustion of the fuel used to heat the flash boiler, as well as to increase the output of steam and hot air from the steam generating apparatus.

In yet another aspect of the invention, the steam head containing the steam generating apparatus is provided with an outlet having an elliptical or oval shape to concentrate the steam and hot air to the target area.

In yet another aspect of the invention, the steam head is provided with a floating inner barrel. The inner barrel is attached to the outer barrel at only one end, preferably the exit end. It fits snugly but floats within the sleeve of the outer barrel at the other end—the intake end. The allows for heat expansion as the inner barrel lengthens further than the outer barrel due to higher temperatures to which it is exposed.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are illustrated in the attached drawings in which:

FIG. 1 is a perspective view of a preferred embodiment of an apparatus for controlling undesired pests according to the present invention having an applicator wand and a wheeled cart arrangement;

FIG. 2 is a perspective view of the handle and trigger assembly of the applicator wand of FIG. 1;

FIG. 3 is a perspective view in cross section of the trigger valve assembly of the applicator wand of FIG. 1;

FIG. 4 is a cross section view of the trigger valve assembly of FIG. 3 in the closed position;

FIG. 5 is a cross section view of the trigger valve assembly of FIG. 3 in the open position.

FIG. 6 is a perspective view of the flow control valve of the applicator wand of FIG. 1;

FIG. 7 is an exploded perspective view of the flow control valve of FIG. 6;

FIG. 8 is an illustration of the operating positions of the flow control valve of FIG. 6;

FIG. 9 is a perspective view of the steam nozzle of the applicator wand of FIG. 1;

FIG. 10 is a cross section view of the steam nozzle of figure 9;

FIG. 11 is a perspective view of a preferred embodiment of an applicator head of the present invention;

FIG. 12 is an end elevation view of the applicator head of FIG. 11;

FIG. 13 is a side elevation view in cross section of a further preferred embodiment of an applicator head of the present invention;

FIG. 14 is a perspective view of a broad head applicator head of the present invention;

FIG. 15 is a side elevation view in cross section of the broad head applicator head of FIG. 14; and

FIG. 16 is a side elevation view of the broad head applicator head of FIG. 14 attached to a cart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the apparatus of the present invention generates a blast of hot air and at least one of steam, hot water or hot water vapor from an applicator head containing a flash boiler heated by a burner, the flash boiler being located in the apparatus adjacent to the outlet to apply the blast to a target area. The apparatus is useful for many applications requiring a blast of hot air and steam, hot water or hot water vapor such as controlling pests through the application of hot air and steam, hot water or hot water vapor directly to the pests only as needed. Other possible uses include a steam cleaner for surfaces not susceptible to heat damage or for heat activation of other materials such as detergents or cleansers or other uses as set out below. Preferably, the apparatus is for controlling pests, particularly unwanted vegetation; however, the apparatus may also be used to control other pests, such as insects, microbial infestations, invertebrates such as mollusks or mussels, etc. The apparatus preferably has an applicator wand for delivery of the heat and steam, hot water or hot water vapor to the vegetation and is characterized by the wand being provided with an applicator head having a steam generator, preferably a burner assembly and a flash boiler, located at the end of the wand, adjacent to or in close proximity to the target area of application. The apparatus has a water supply and fuel supply for the burner and steam generator, the water and fuel being supplied to the burner and steam generator through suitable hoses.

A preferred embodiment of the apparatus of the present invention, is illustrated in FIG. 1. The apparatus utilizes an applicator wand 10 and a cart arrangement 12 to supply the fuel and water to the applicator wand 10. The cart 12 is provided with a frame arrangement 14 including a handle portion 16. Attached to the frame 14 are wheels 18 and 20 to allow the cart to be easily moved. Preferably, wheels 18 are relatively large wheels attached to either side of the frame 14 and wheel 20 is a smaller wheel pivotally attached to the front of the frame 14. Pivotable wheel 20 allows the operator to easily turn the cart while providing for enhanced stability due to the presence of the three wheels. Cart 12 also is provided with a water tank 22 sized to hold sufficient water for operation of the apparatus. Cart 12 is also provided with a holder for a fuel container, preferably a propane cylinder 24 which connects to the applicator wand 10 through a suitable fuel hose 26. The cart 12 is also provided with a control module 28 which includes a water pump connected between the water tank 22 and a water supply hose 30 which supplies the water to the applicator wand 10. Also included within the control module 28 are a source of energy for the water pump and control and feedback circuitry and displays to allow an operator to monitor the operating parameters of the apparatus. The cart 12 is also provided with a means to hold the applicator wand 10 which includes a first means 32 on which the end of the applicator wand 10 rests and a second means such as bracket 34 to support the applicator head 36. The cart 12 may also be provided with a means for holding a clipboard 38 or other paper for reference by the operator.

The applicator wand 10 is designed for one hand operation and consists of a forearm brace 40, a pistol style grip 42 with trigger controls, and a suitable dimensioned metal tube or pipe 44 carrying the fuel and water lines and connected to the applicator head 36 containing the burner assembly and steam generator. The applicator head 36 preferably has an insulated, reflective, metallic wall 46 to maximize and focus heat production. The applicator head 36 is dimensioned to produce the desired steam and heat output while being able to be manipulated by the user. Preferably, the applicator head 36 is tubular having an inner diameter of between about 2 and 6 inches, more preferably about 2 to 4 inches, and a length of between about 12 and 30 inches, more preferably about 18 to 24 inches, depending upon application, burner size and desired steam and hot air output.

Referring to FIG. 2, the fuel line 26 is connected to the handle 42 of the applicator wand 10 through a suitable connection such as a quick connect fitting 50. Preferably, for ease of handling, the fuel line 34 and water hose 30 are joined together along most or all of their length. In addition, one or more electrical lines may be provided to provide power to any electrical components associated with the applicator wand 10 as well as to provide for data transfer between any sensors or controls which may be part of the applicator wand 10 and the control module on the cart 12. A first valve 52 located in the handle downstream from the quick connect fitting 50 regulates the fuel flow to allow for fuel shut off and set the maximum fuel flow. A control valve 54 controlled by the trigger control 56 is also provided in the handle. The control valve 54 has two positions—a “STAND BY” position, which permits a reduced fuel flow to maintain a pilot light in the burner as will be explained below and to provide low heat output, and an ON position when the trigger control 56 is activated which permits full fuel flow and maximum heat. With this type of valve a control is provided to regulate the flow of fuel in the “STAND BY” position to set the pilot light. From the control valve 54, a fuel line 60 then travels along the pipe 44 of the applicator wand 10 to the burner head 62 of the applicator head 36.

The water hose 30 is connected to a trigger control valve 64 controlled by the trigger control 56. The trigger valve 64 provides reduced water flow in the “STAND-BY” position, and permits water flow in the “ON” position as will be described in detail below. From the trigger control valve 64, a water line 66 is attached to a flow control valve 68 designed to set the flow of water to the flash boiler as will be described below. From the flow control valve 68, the water travels down a water line 70 along the applicator pipe 44 to a flash boiler arrangement within the applicator head 36. The details of the flash boiler arrangements are set out in U.S. Pat. No. 7,100,540, the disclosure of which is incorporated herein by reference.

In many of the applications where steam is used for pest control, it is desirable to provide for a continuous flow of water to the flash boiler, even in STAND-BY mode. By providing a small trickle of water to the flash boiler, the response time when the switch is pressed to the ON position is reduced and the life of the flash boiler is extended. The continuous small flow of water is provided by a valve arrangement having a suitable means to feed a small amount of water to the flash boiler at all times. One means of accomplishing this is utilizing the trigger control valve 64 and flow control valve 68 of the present invention, both of which are “leaky” valves as will be explained below.

The details of the preferred embodiment of the trigger control valve 64 of the present invention are illustrated in FIGS. 3 to 5. Trigger control valve 64 has an inlet 72 and an outlet 74. Within the valve 64 is a chamber 76 in fluid connection between the inlet 72 and the outlet 74. Within the chamber 76, a sealing surface 78 is provided which mates with a corresponding sealing surface 80 on a poppet 82 which is maintained in the closed position by a suitable biasing means such as spring 84 as illustrated in particular in FIG. 4. When the sealing surfaces 78 and 80 abut, the valve 64 is in the closed position. Poppet 82 is connected to an actuating means 86 which is moved by the action of the trigger control 56. Actuating means 86 slides within a channel 88 of the body of the valve 64 and an 0 ring 90 is provided between the wall of the chamber 76 and the exterior of the actuating means 86 to prevent fluid leakage into the channel 88 and hence out of the valve 64.

In order to provide for the “leaky” or slow flow characteristic of the trigger control valve 64, sealing surface 78 is provided with a leak channel 92 which allows for a low flow of water through the channel 92 when the poppet 82 is in the closed position. As there may be some collection of debris in the leak channel 92, a further cutout 94 may be provided to flush any debris from the leak channel 92 when the poppet 82 is opened.

In some applications, it is desirable that a higher proportion of hot air to steam and hence higher treatment temperatures be applied, which can results in a higher rate of operation. In other applications such as more flammable situations, a higher proportion of steam and hence a lower treatment temperature is desired. The proportion of steam to hot air in the output of the apparatus of the present invention can be adjusted by the amount of water being provided to the flash boiler. The higher the amount of water provided to the flash boiler, the more steam generated as the water is converted to steam. Thus by adjusting the flow rate of the water to the flash boiler, the relative amounts of steam and hot air in the output of the apparatus can be regulated.

There are a number of ways in which the flow of water to the flash boiler and hence the ratio of hot air and steam in the output can be adjusted. This can be accomplished by providing a flow control valve 68 with a variable adjustment to allow for complete control over the flow of water. In this way, the operator can select the flow rate to provide the optimum ratio for a particular application.

In the preferred embodiment, the flow control valve 68 is a face seal rotary valve with elliptical orifices. As shown in FIGS. 6 to 8, flow control valve 68 has an inlet 94 and an outlet 96. Outlet 96 is provided with a recessed surface 98 having a first elliptical opening 100. Flow control valve 68 is provided with an adjustment knob 102 to allow the operator to adjust the flow rate of the fluid through the flow control valve 68. Adjustment knob is attached to a face seal plate 104 which is biased in sealing engagement with the recessed surface 98 of the outlet 96 by spring 106. In order to control the degree of rotation of the face seal plate 104, the face seal plate 104 is provided with a semi-circular groove 108 having a stop 110 contained therein, the stop 110 is attached to a back plate 112 held in position by the spring 106.

Face seal plate 104 is provided with a second elliptical opening 114 which in the open maximum flow position shown as D generally aligns with the first elliptical opening 100 on the recessed surface 98 of the outlet 96. As illustrated in FIG. 8, the center of rotation 116 of the second elliptical opening is located near one of the ends of the elliptical opening. FIG. 8 illustrates the relative positions of the two elliptical openings 100 and 114 at various positions of the flow control valve 68. Position A illustrates the minimum flow position, position B illustrates a medium flow position, position C illustrates the second elliptical opening 114 approaching maximum flow position and position D illustrates maximum flow position. As can be appreciated, a slow flow of fluid will pass through the flow control valve 68 even in the lowest setting, and through rotation of the second elliptical opening, a variable flow rate of fluid up to the maximum flow rate may be achieved.

For most applications, the actual ratio of steam to hot water may not be critical, rather the presence of a certain amount of hot water in the output may be advantageous. It is therefore preferred if a multi-position switching means is provided to allow the operator to select a high water, high steam and perhaps intermediate positions. For example, the flow control valve 68 is calibrated for the desired output settings and the adjustment knob 102 of the valve 68 is provided with markings to allow the user to easily select the desired setting. Thus the valve 68 is calibrated for a high steam output and the adjustment knob position for this setting is indicated. Similarly, a high water setting is determined and the adjustment knob position indicated. One or more intermediate positions between these two settings may be also provided if desired.

In another aspect of the present invention, the flash boiler of the steam generating apparatus is provided with a steam nozzle arrangement as shown in FIGS. 9 and 10. Steam nozzle 120 has an inlet 122 which connects to the end of the flash boiler (not shown) and a plurality of outlets 124 connected to one another by channel 126. In the embodiment illustrated there are three such outlets 124 however other numbers of outlets, particularly a larger number may be provided. By providing the outlets 124 in a fan out arrangement, it has been found that the steam generated by the flash boiler is more diffused and air flow through the applicator head 36 is enhanced. This results in increased efficiency of the apparatus and reduced CO emissions from incomplete combustion.

It is preferred if the steam nozzle 120 is centrally located in the lower opening of the applicator head 36. In order to achieve this, mounting spacers or fins 128 are provided attached to the body of the steam nozzle. Spacers or fins 128 are sized to fit within the opening of the applicator head 36 to maintain the steam nozzle in the desired position within the applicator head 36. The embodiment illustrated in the figures has four such spacers or fins 128, however fewer or more such structures may be provided depending upon the size and configuration of the applicator head.

In another aspect of the present invention, a new design for the applicator head 36 has been developed as illustrated in FIGS. 11 and 12. In operation, the apparatus of the present invention is used for weed control in cracks and crevices of hard surfaces such as concrete, asphalt, etc as is found on sidewalks, pathways, roads, etc. The operator uses the apparatus by pushing it along the hard surface with the wheel 48 rolling along the surface. As can be seen in FIG. 1 as well as FIGS. 11 and 12, the lower end of the applicator head 36 is angled to maintain a close relationship with the surface as the applicator wand 10 is being pushed along. It has been discovered that if the end of the applicator head 36 is modified to an enhanced oval or elliptical shape, the efficiency of the apparatus is improved, particularly in terms of better contact with the treatment surface. As illustrated in FIGS. 11 and 12, the applicator head 36 is provided with a flare out end 130 which provides an oval or elliptical shape to the end as shown in FIG. 12.

Another improvement to the steam generating apparatus is the provision of an air blower 58 to increase the volume of air flowing through the steam generating apparatus to increase the combustion of the fuel used to heat the flash boiler, as well as to increase the output of steam and hot air from the steam generating apparatus. Such an arrangement has been illustrated in FIG. 2 where an air blower 58 is provided, the outlet of the air blower 58 being provided with tubing 59 to feed the air into the interior of the applicator head 36 to improve the operation of the steam generating apparatus. By increasing the air flow through the applicator head, the size of the combustion chamber of the applicator head may be reduced relative to those shown in my previous U.S. Pat. No. 7,100,540. This results in a lighter, more compact and efficient apparatus.

A further embodiment of an applicator head of the present invention is illustrated in FIG. 13 generally indicated by the numeral 200. The applicator head has an inner barrel 202 separated from an outer barrel 204 by suitable insulation 206. The inner barrel 202 is attached to the outer barrel 204 at only one end, preferably the outlet end 208. At the inlet end 210, the inner barrel 202 is not attached but floats within the outer barrel 204. The allows for heat expansion of the inner barrel as the inner barrel lengthens further than the outer barrel due to higher temperatures to which it is exposed.

A broad head applicator head for providing a wide treatment area is illustrated in FIGS. 14 to 16 generally indicated by the numeral 300. The broad head applicator head 300 has an enclosed box 302 dimensioned to allow a wide treatment area which can be up to 6 feet. Preferably the enclosed box 302 will be 2 feet by 3 feet or 3 feet by 6 feet, depending upon the application. Attached to the upper surface 304 of the enclosed box 302 are a plurality of individual flash boilers 306 each having a burner 308 and steam generator 310. The flash boilers 306 are provided every 6 to 24 inches across the width of the upper surface 304 of the enclosed box 302, depending upon the size of the flash boiler 306, size of the enclosed box 302 and application.

The broad head applicator head 300 may be attached to the front of a cart similar to that as described above, or as illustrated in FIG. 16, it may be attached to a utility vehicle such as a GATOR or similar vehicle. The flash boilers 306 are provided with water and fuel from suitable water tank 310 and fuel container 312 connected to the flash boilers 306 by suitable hoses. The flow of the water and fuel to the flash boilers are controlled by a suitable control module similar to that described above which includes a water pump, a source of energy for the water pump and control and feedback circuitry and displays to allow an operator to monitor the operating parameters of the apparatus. The control module also includes suitable flow control valves for the water and fuel as described above.

The broad head applicator head is preferably provided with a wheel or skid at the front thereof to space the enclosed box slightly above the surface to be treated to allow the broad head applicator head to pass over the surface to be treated. This embodiment of the applicator head is of particular use on gravel and interlocking paths and generally open space, non-linear weed control.

The present invention provides for numerous improvements in steam generating apparatus for pest control, resulting in more efficient operation. The improvements make the operation of the apparatus easier for the user and result in some cases in an apparatus having a reduced weight which also increases ease of operation.

In addition to the uses of the various improvements to steam generating apparatus as described above, it will be appreciated that certain of the described components may have broader application. For example, the “leaky” valves described above have utility in other applications where it would be advantageous to have a continual low flow of fluid through the valve at all times. In particular, applications where the valves controlling the fluid flow are exposed to extremes in temperature, particularly temperatures below freezing could benefit from such valves. The low flow rate at all times through the valves could prevent the fluid within the lines or the valves itself from freezing and causing potential damage. Other uses for these and other components described above will be apparent to those skilled in the art.

Although various preferred embodiments of the present invention have been described in detail, it will be appreciated by those of skill in the art that variations may be made thereto without departing from the spirit of the invention. 

1. An apparatus for generating at least one of steam, hot water and hot water vapor along with air heated by a burner for application to unwanted vegetation, the apparatus comprising a wheeled cart supporting a water container, a control module, a holder for an applicator wand and a fuel container, the applicator wand comprising a holding means and an applicator head coupled to the holding means, the applicator head comprising a housing, an inlet and an outlet to define a cavity to accept a flash boiler adjacent the outlet, the flash boiler comprising a steam generator and a burner for heating the steam generator, a first elongate hose connecting the water container to a first control located on the applicator wand, the first control controlling and supplying a flow of water to the steam generator, and a second elongate hose connecting the fuel container to a second control located on the applicator wand, the second control controlling and supplying a flow of fuel to the burner, both the first and second controls being controlled by a single switch, such that when said switch is activated, fuel and water are supplied essentially simultaneously to said flash boiler and a blast of heated air and at least one of steam, superheated steam, hot water and hot water vapor is urged from the outlet to the unwanted vegetation, the control module of the wheeled cart including a water pump to supply water to the applicator wand from the water tank, a source of energy for the water pump and control and feedback circuitry and displays to allow an operator to monitor the operating parameters of the apparatus.
 2. A flow control and flush valve for a steam generating apparatus for weed control, which allows for a simple means of controlling the volume of water flowing through the system, the flow control valve comprising a first fixed elliptical orifice and a second rotating elliptical orifice, the center of rotation of the second elliptical orifice being located adjacent one end of the orifice, the rotation of the rotating orifice varying the overlapping area between the fixed orifice and the rotating orifice to allow for control of the volume of water flowing through the overlapping orifices.
 3. A trigger control valve having a bypass channel such that a small flow of fluid passes through the valve when the valve is in the closed position, the trigger control valve being provided with an inlet and outlet and a spring biased poppet, which seals the outlet when the valve is in the closed position, the sealing surface of the valve against which the poppet rests being provided with a channel to allow for a low flow of water in the closed position.
 4. A steam nozzle for a steam generating apparatus for weed control, the steam nozzle aiding in diffusing the steam and accelerating the airflow through the steam generating apparatus, the steam nozzle comprising an inlet and a plurality of outlets to provide for the diffusion of the steam from the steam generating apparatus.
 5. The steam nozzle according to claim 4 wherein the steam nozzle is centrally mounted within the outlet of the steam generating apparatus by a plurality of spacers or fins located between the exterior of the steam nozzle and an interior wall of a steam head of the steam generating apparatus.
 6. The steam generating apparatus according to claim 1 wherein the steam generating apparatus is provided with an air blower to increase the volume of air flowing through the steam generating apparatus to increase the combustion of the fuel used to heat the flash boiler, as well as to increase the output of steam and hot air from the steam generating apparatus.
 7. The steam generating apparatus according to claim 1 wherein the steam head containing the steam generating apparatus is provided with an outlet having an elliptical or oval shape to concentrate the steam and hot air to the target area. 